No Bit Memory But Global Data Blocks - Siemens S7-1200 Programming Manualline

4 Hardware-Independent Programming

4.2 No bit memory but global data blocks

Character type
Field
Structure
1)
For S7-1500 the ARRAY data type is limited to 64 bit instead of 16 bit
Table 4-3: Parameter types for formal parameters that are transferred between blocks
Pointer
Blocks
PLC data types
1)
For optimized accesses, only symbolic addressing is possible
2)
For S7-1200/1500 the TIMER and COUNTER data type is represented by
IEC_TIMER and IEC_Counter.
4.2 No bit memory but global data blocks
Advantages
Optimized global DBs are clearly more powerful than the bit memory address
area that is not optimized for reasons of compatibility.
Recommendation
The handling with bit memory is problematic, since every controller has a bit
memory address area with a different size. Do not use bit memory for the
programming but always global data blocks. This is how the program can
always be used universally.
Programming Guideline for S7-1200/1500
V1.2, Entry ID: 81318674
Description
LDT
(L_DATE_AND_TIME)
STRING
ARRAY
STRUCT
Description
POINTER
ANY
VARIANT
TIMER
COUNTER
BLOCK_FB
BLOCK_FC
BLOCK_DB
BLOCK_SDB
VOID
PLC Data Type
S7 - S7-1200
300/400
S7 - S7-1200
300/400
2)
S7-1500
1)
S7-1500
1)
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